Is a word an anagram of itself?
(I lean towards "yes". I would then define the word itself as the trivial anagram; the anagram that can be found by performing 0 character shifts.
This would give anagrams a lovely mathematical property: It would make the relation "A is an anagram of B" an equivalence relation! This would also mean that the set of all strings has partitions, each of which contains all strings that are anagrams of each other.)